JPH0380596B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a spot welding method using a laser beam.

[Prior art]

Because the aligned focus of the laser beam produces high output power, lasers are effectively used for general metal processing and welding processes that require penetration effects. The advantage of laser beams is that they can easily propagate through the air over large distances with little loss of energy;
It is possible to time-divide supply to a large number of work stations distributed in a work place. Similarly, if a laser is used, spot welding can be performed continuously throughout a large workpiece, so it can be used, for example, for primary welding of overlapping metal plates such as the body of an automobile. Conventionally, resistance welding has been used in two ways for this type of welding. One is a method in which each location is welded separately, which requires welding equipment such as a fixture and its support, a cable with a large cross section, a transformer, a power supply and operation device, etc. It requires equipment. The other method is to use one or more robots equipped with welding equipment, in which one robot performs welding work at several locations. In this method, a large number of welding equipment is moved at once by a robot in the shortest possible time within the limits of the mechanical stress of the moving elements.

Using a laser beam allows energy dispersion from a single source, so if the laser beam is dispersed into multiple parallel laser beams and each laser beam is projected to a focus adjustment device that corresponds to the position, superimposed processing can be performed. The focusing device, located vertically above the workpiece, focuses the laser beam onto the workpiece, and a high power focused focus with a penetration effect causes the overlapping workpiece to be welded at multiple locations. For example, as shown in FIG. 1, a plurality of plane mirrors 1 (three in the illustrated example) that can be freely moved in and out on the optical axis of the laser beam are arranged in a row, and the laser beam 2 irradiated from the generator 3 is A focus adjustment device 4 that is sequentially reflected by each plane mirror 1 and located vertically below each plane mirror 1;
5 and 6 sequentially, the welding work can be simplified by eliminating the work of moving the welding equipment, etc., compared to the method using a robot as described above. Moreover, in such a method, the welding part 7 having a sufficient cross-sectional area for the superimposed workpiece 7 to be welded
₁ is an important factor, but since it is technically and economically impossible to form a large number of separate welds 7 ₁ , the laser beam aligned on the superimposed workpiece 7 is By drawing a circular orbit at the focal point, the joint is strengthened by increasing the cross-sectional area of the welded part ₇₁ . For this reason, motors 4 ₁ , 5 ₁ , 6 ₁ are connected to each welding head, and focus adjustment devices 4 and 6 1 are connected to each welding head.
Conventionally, a method has been used in which movable members such as lenses and concave mirrors are mounted in 5 and 6, and the welding head and movable members are rotated by a motor to draw a circular trajectory at the matching focus of the laser beam. . However, according to this conventional method, it is necessary to install a rotary drive device and an operating device for each of the focus adjustment devices 4, 5, and 6, resulting in an increase in the size of the overall structure of the welding device, and a plane mirror for the laser beam. Since it is necessary to control the operation of each drive device based on the reflection position etc., there are drawbacks such as a complicated mechanism.

[Means to solve the problem]

This invention has been made to solve the above-mentioned drawbacks, and aims to provide a spot welding method using a laser beam that can simplify the structure of the welding device as a whole. The optical axis of the laser beam to be processed is controlled to move, and the moving laser beam is sent to a stationary focusing device, and the laser is aligned on the workpiece by the focusing device so that the movement trajectory corresponding to the movement mode of the moving laser beam is controlled. This is where the image is drawn at the focus of the beam.

Further, according to the method of the present invention, the laser beam emitted from the generator is moved in parallel or rotationally scanned with respect to its emission optical axis. Then, the laser beam is moved and scanned on one plane.

[Action and effect]

In this invention method, a static focus adjustment device is used, and the laser beam itself is moved and scanned before entering the focus adjustment device, so movable members etc. provided in each focus adjustment device are moved. There is no need to operate to move the focal position of the beam, and the entire device can be made smaller and the operation can be simplified.

Note that the focus adjustment device uses various lenses and mirrors whose shapes and dimensions are adjusted to align the focal point of the beam to a desired position depending on the beam diameter and scanning path of the incident laser beam. The selection depends on the power of the laser beam used.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

The apparatus shown in FIG. 2 is a laser welding apparatus that sequentially forms circular spot welds between superimposed workpieces 8 and 9.

The laser beam 11 emitted from the laser generator 10 has its optical axis aligned with the axis 13 by the device 12.
parallel to and rotated about the axis 13. A plurality of plane mirrors 15, 16, 17 are arranged on the shaft 13.
are arranged. Each of these plane mirrors can be repositioned on-axis and off-axis, and when positioned on-axis, the laser beam 1 emitted from the device 12
4 is reflected thereon and guided to focus adjustment devices 15 ₁ , 16 ₁ , 17 ₁ corresponding to each of the plane mirrors 15 , 16 , 17 , the axial position of which is set.

The laser beam 18, which is reflected by the plane mirrors 15, 16, 17 and rotates around the axis 19, enters the focus adjusting device 15 ₁ , 16 ₁ , 17 ₁ where the focus is adjusted, and the superimposed workpieces 8, 9 Its focus is on point 20 on the top surface. This point 20 draws a circular trajectory corresponding to the circular trajectory of the incident beam 18 on the upper surface of the superimposed workpiece. In this way, the superimposed workpieces 8 and 9 are fused together along their contact surfaces by the laser beam whose focal point gradually draws a circular orbit on the upper surface of the overlapping workpieces 8 and 9, and the diameter of the circular orbit drawn by the focal point 20 A weld point is formed having a diameter that substantially corresponds to the diameter of the weld.

By thus constituting the focusing device from only stationary elements, its structure and assembly are simplified and, above all, its bulk is reduced, so that the installation spacing of the device and thus the formation spacing of the welding points can be reduced. This makes it possible to strengthen the joint between the superimposed workpieces, and also to ensure sufficient space for positioning the superposition workpieces and operating tools such as grips.

In FIG. 2, the laser beam is rotated by the device 12 parallel to the axis 13 and around the axis 13, but the laser beam sent out from the device 12 is rotated about the axis 13, and the laser beam is rotated in a circular orbit or around the axis 13. It is also possible to draw other suitable trajectories.

FIG. 3 shows one embodiment of the device 12. According to this device 12, a beam 11 emitted from a generator 10 is continuously reflected by two plane mirrors 21 and 22. These two plane mirrors 21, 22
have one end pivoted on two orthogonal shafts 21 ₁ and 22 _1, respectively, and the other end connected to gears 24 and ₂₅ driven by an electric motor 23 via mechanical transmission devices 24 ₁ and 25 1. Each is connected. Therefore, the operation of the electric motor 23 causes 2
The two plane mirrors 21 and 22 are swung around a pivot axis,
The swing angular velocity of both plane mirrors 21 and 22 is the same, and
Under the condition that the phases of both plane mirrors 21 and 22 are different by 90 degrees, the axis 13 becomes the rotation axis of the laser beam 14. That is, rotational movement of the beam 14 about the axis 13 is obtained while the translation of the beam 11 entering the device 12 and the beam 14 exiting the device 12 is maintained. Naturally, by changing the conditions such as the angular velocity and phase, the laser beam 14 can be caused to take a different movement form.

FIG. 4 shows focus adjusting devices 15 ₁ , 16 ₁ , 17 ₁ composed of a plurality of mirrors. In the figure, the laser beam 14 sent from the device 12 to the first plane mirror 26 is reflected by the plane mirror 26 and guided onto a polygon mirror 27 composed of a large number of concave mirrors 27 ₁ . The laser beam guided by each concave mirror 27 ₁ is then focused on the upper surface of the superimposed workpiece to be welded. In addition, the focus of the laser beam adjusted by the adjacent concave mirror 27 ₁ is
The polygon mirror 27 is configured to draw a circular locus on the surface of the superimposed workpiece. Therefore, beam 1
4 makes one revolution around the axis 13, the beam 14 reflected by the plane mirror 26 is successively directed onto each adjacent concave mirror ₂₇₁ , and the focus of the beam 14 is focused on the plane 28 at successive intervals. As a result, the spot welds formed on the focal position ₂₈₁ are integrated, and one spot weld 29 as shown in FIG. 8 is formed between the superimposed workpieces. Since this spot weld 29 has a suitable joint area, a strong connection between the two processed parts is ensured.

Polygon mirror 27 as shown in FIGS. 4 to 6
According to the method using a spot weld 29 formed by a laser beam scanned in a circular orbit,
As shown in FIG. 9, a series of spot welds 30 are formed in a chrysanthemum pattern in which they overlap. However, if a mirror having a reflective surface such as an annular shape that can adjust the focus of the beam on the same plane according to the incident angle of the beam is used instead of the polygon mirror 27, it is possible to create a seamless fusion between the superimposed workpieces. It is also possible to form tangent continuous lines, for example continuous circular lines. In this case, the fusion weld grows radially along the circular line due to cumulative heat conduction, so that both workpieces are grown along the circular surface 31 having a diameter approximately equal to the diameter of the focal scanning circular path of the laser beam. will be welded. An example of this type of mirror is shown in FIG. The reflecting surface 32 ₁ of the mirror 32 is configured as a toric concave surface, and the incident laser beam that is rotated and scanned around the axis 13 is continuously focused on a plane 33 by the mirror 32, and its focal trajectory is circular on the plane 33. It's like drawing a line.

In this invention, it is also possible to use a lens as a static focusing device. This is illustrated in FIG.

The lens 34 has a convex upper surface 34 ₁ that receives a moving and scanned projection laser beam, and a polygonal pyramid-shaped lower surface 34 ₂ through which the laser beam passes.
It consists of a convex or concave lower surface 34.
_2. The laser beam passing through each surface is focused on the same plane, and the focus is configured to draw a discontinuous circular line on the plane. Of course,
It is also possible to draw a continuous circular line on the focus adjustment surface, and in this case, as illustrated in FIG _.
and a lower circle 36 ₂ made of a conical surface having a plane or curved surface (convex or concave) as its parent surface, which allows the passing beam to draw a circular orbit.

When it is desired to form a weld line instead of a spot weld on the superimposed workpiece, a laser beam 38 emitted from a laser generator is first moved and scanned on a plane mirror 37, as shown in FIG. This beam movement scanning is shown in Fig. 2 or 3.
The method shown can be carried out with an adaptation for linear motion scanning. The laser beam 38 projected onto the plane mirror 37 is reflected, guided onto the polygon mirror 39, and focused onto a plane. This polygonal mirror 39 is composed of a series of concave mirrors 39 ₁ , for example, so that the laser beam 38 moved and scanned on the plane mirror 39 is sequentially scanned by adjacent concave mirrors 39 _{1 .}
, and a discontinuous line is drawn on the plane by the focal point 40.

[Brief explanation of drawings]

The drawings show such embodiments,
Fig. 1 is a schematic diagram of a conventional welding device, Fig. 2 is a side view of the device used in the present invention, and Fig. 3 is a perspective view showing an embodiment of a device for rotating and scanning a laser beam. , FIG. 4 is a perspective view of an apparatus equipped with a concave polygon mirror, FIG. 5 is a front view of the concave polygon mirror of FIG. 4, FIG. 6 is a sectional view taken along the line - of FIG. 5, and FIG. The figure is a side view showing a focus adjustment device consisting of a multifaceted lens, FIG. 8 is a sectional view showing a spot weld formed according to the present invention, FIG. 9 is a plan view of the same, and FIG. 10 is a spot weld in another embodiment. , and FIG. 11 is a perspective view of another embodiment of the focusing mirror.
FIG. 12 is a perspective view of another embodiment of the focus adjustment lens;
FIG. 13 is a perspective view of a concave polygon mirror for focusing, which is made up of a series of concave mirrors. 10... Laser beam generator, 11... Laser beam, 13... Axis, 14, 18... Moving laser beam, 15, 16, 17... Plane mirror,
15 ₁ , 16 ₁ , 17 ₁ ... focus adjustment device, 34,
36...Lens.

Claims (1)

[Scope of Claims] 1. A method for guiding a laser beam emitted from a laser beam generating device to at least one device, and aligning the focus of the laser beam on a workpiece by the device, the method comprising: A laser beam emitted from the apparatus is moved and scanned, and the moving and scanned laser beam is guided to a stationary focusing device to align the focus of the laser beam on the workpiece and to direct the laser beam to the focusing device at the aligned focus. A spot welding method using a laser beam, characterized in that a movement trajectory is drawn on a workpiece in accordance with the movement scanning of a guided laser beam. 2. A spot welding method using a laser beam according to claim 1, characterized in that the laser beam emitted from a laser beam generator is scanned in parallel with its radiation axis. 3. A spot welding method using a laser beam according to claim 1 or 2, characterized in that the laser beam is rotated and scanned. 4. A spot welding method using a laser beam according to any one of claims 1 to 3, characterized in that the laser beam is moved and scanned within one plane.